Copolyester resin for solventborne coating and coating composition comprising the same

ABSTRACT

Disclosed is a copolyester resin having number average molecular weight over 5,000 for solventborne metal coating binder, which has superior gloss retention and color stability after long term outdoor exposure, and a coating composition comprising the same. The copolyester has excellent weatherability and color stability. The copolyester resin is prepared through the polycondensation of an acid component comprising 60–90 mol % of aromatic dicarboxylic acid selected from the group consisting of isophthalic acid, C1–C2 alkylester of isophthalic acid, phthalic acid, C1–C2 alkylester of phthalic acid, phthalic anhydride, and mixtures thereof, and 10–40 mol % of cycloaliphatic dicarboxylic acid selected from the group consisting of 1,2-cyclohexane dicarboxylic anhydride, 1,2-cyclohexane dicarboxylic acid, C1–C2 alkylester of 1,2-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, C1–C2 alkylester of 1,4-cyclohexane dicarboxylic acid, and mixtures thereof, an alcohol component comprising 60–100 mol % of 2,2-dialkyl-1,3-propandiol and 0–40 mol % of a polyvalent alcohol and 0–5 mol % of a polyvalent alcohol or acid.

The present invention relates, in general, to a copolyester resin forcoating and, more particularly, to copolyester resin that is of superiorstability against UV light and hydrolysis. This resin can be useful as abinder for an outdoor-durable top-coating paint for exterior finishmaterials by virtue of its high weatherability and coat hardness.

Of coating compositions for exterior finish materials, anoutdoor-durable top-coating paint is required to be superior inweatherability because it is exposed to UV light and rain for a longperiod of time. Such exposure causes the binder resin of the paint to bedegraded, so that the paint coat becomes dull in gloss and discolored ina short term. In addition, the paint coat undergoes chalking and isdegraded or cracked with the passage of a long period of time. In mostcases, thus, the exterior finish materials need repainting regularly.

In order to prevent such coating aging, the binder resin used must haveexcellent anti-UV degradability (resistance to UV degradation) as wellas anti-hydrolysis.

Widely used at recent are alkyd resin and vinyl resin. The paints usingthese resins as binders show good mechanical properties, such ashardness. However, the alkyd resin paint and vinyl resin paint aregreatly insufficient of weatherability and poor in processability, sothat they have many limitations and much difficulty in practicalapplication.

At present, much attention is paid to silicon alkyd based resins andfluorine resins as binders for exterior finish materials, such as steelplates. Besides being very poor in processability, silicon alkyd basedpolyester resins suffer from a significant problem in that siliconpowders blow upon painting to cause cratering. Thus, it is difficult towork with the silicon alkyd based polyester resins. In addition, theyare found to do not greatly improve in weatherability. Fluorine resinpaints are far superior in weatherability, but show low hardness onaccount of their chemical structures in addition to being poor inprocessability. What is worse, they are very expensive. So, they arelimited in use.

For these reasons, many attempts have been made to provide highweatherability for pure polyester resins. To date, however, only alittle improvement has been brought about in weatherability of purepolyester resins, and their processability does not come up to a desiredlevel owing to their highly branched structures. For instance, U.S. Pat.No. 5,620,801 describes a copolyester for solvent based coating materialwhich attempt providing UV stability, but this material shows badprocessability because it has not only lower level of molecular weightbut also high branched structure using preferably 5 to 15 mole % oftrifunctional monomer, calculated on hydroxy or acid compounds. U.S.Pat. No. 5,376,460 also describes a solventborne copolyester comprisedof over 50 mo % of cycloaliphatic acid component for outdoor durablecoating, but the coatings obtained according to this patent have lowerhardness and bad hydrolysis resistance caused from its lower contents ofaromatic materials.

With the background in mind, the present invention has an object ofproviding copolyester resin compositions for coating, which are superbin weatherability as well as show excellent paint film hardness andpress processability.

Knowledge of the structural characteristics of copolyester allowsmodification and adaptation leading to this invention. As a result ofthe intensive and thorough research on a copolyester-based coatingcomposition, repeated by the present inventors, it was found that,together with a completely saturated cycloaliphatic dicarboxylic acid, acombination of 2,2-dialkyl-1,3-propanediol, free of beta-hydrogen,containing 5–9 carbon atoms, aromatic dicarboxylic acid, andcycloaliphatic glycol can be synthesized into a copolyester resin whichis of superior stability against UV light and hydrolysis. When beingformulated with components for a coating composition, this resin wasalso found to provide the coating composition with the necessaryhardness, gloss and anti-photolysis for top-coating paints. In addition,the copolyester resin can be polymerized to a sufficient molecularweight to show high press processability.

In an aspect of the present invention, there is provided a copolyesterresin, prepared by polycondensing the following components:

-   (a) an acid component comprising 60–90 mol % of aromatic    dicarboxylic acid selected from the group consisting of isophthalic    acid, C1–C2 alkylester of isophthalic acid, phthalic acid, C1–C2    alkylester of phthalic acid, phthalic anhydride, and mixtures    thereof, and 10–40 mol % of cycloaliphatic carboxylic acid selected    from the group consisting of 1,2-cyclohexane dicarboxylic acid,    C1–C2 alkylester of 1,2-cyclohexane dicarboxylic acid,    1,2-cyclohexane dicarboxylic anhydride, 1,4-cyclohexane dicarboxylic    acid, C1–C2 alkylester of 1,4-cyclohexane dicarboxylic acid, and    mixtures thereof; and-   (b) an alcohol component comprising 60–100 mol % of    2,2-dialkyl-1,3-propanediol represented by the following general    formula:

wherein R and R′, each is a C1–C4 alkyl group, and 0–40 mol % of apolyvalent alcohol; and

-   (c) a polyfunctional component having functionality three or higher    in an amount of at most 5 mol % based on the total moles of acid and    alcohol components, said polyfunctional component comprising    polyacid and/or polyol.

In another embodiment, in the compound of chemical formula I, R and R′each is a C2–C4 alkyl group and this compound is present in an amount of10–55 mol %.

In another embodiment, the copolyester has an intrinsic viscosity of 0.2dl/g or greater and ranges, in number average molecular weight, from5,000 to 20,000.

In another aspect of the present invention, there is provided asolventborne coating composition comprising such a polyester resin.

The gloss dullness and chalking phenomenon of polyester coatings, whichboth appear with aging of the coatings, are known to be attributed tothe occurrence of photodegradation (particularly, UV degradation) andhydrolysis in the resin component of coating constituents. The UVdegradation is performed in two ways: direct degradation in which UVlight itself participates, and photooxidation. Generally, thephotodegradation of aliphatic materials is progressed in the formermanner while the latter is a main mechanism of the photodegradation ofaromatic materials.

To avoid using aromatic materials, which are of large UV absorptivity,is a means of restraining UV photodegradation. However, the absence ofaromatic materials renders coating compositions too low in glasstransition temperature (Tg) and causes moistures to diffusely transferin the coating compositions, deteriorating the stability againsthydrolysis. Hence, it is necessary to use aromatic materials, but theyare required to have molecular structures that are of so low fluiditythat oxygen diffusion does not easily take place, thereby restrainingoxidation, a main photodegradation mechanism of aromatic materials.

Since aliphatic materials are degraded in a Norrish-II type mechanism bylight, it is recommended that the coating compositions contain as littlebeta-hydrogen as possible.

Also, the presence of a side chain at specific positions of the binderresin makes it difficult for moistures to access ester linkages,assuring the coating composition of stability against hydrolysis. Thesespecific positions that allow the minimization of hydrolysis aresuggested as the “Rule of six” of Newman.

To these ends, a completely saturated cycloaliphatic dicarboxylic acid,or its alkylester or anhydride derivative, is employed as a polyvalentacidic component in preparing copolyester resins of the presentinvention. Also, the copolyester resins comprise an aromaticdicarboxylic acid, or its alkyl ester or anhydride derivative as anotherpolyvalent acidic component. Used as a necessary component, thisaromatic dicarboxylic acid is structurally so low in fluidity as toprevent oxygen and moisture diffusing, thereby providing the hardnessand gloss to a level suitable for top-coating paints.

As for the polyvalent alcohol component for the polyester resin, itcomprises alkylene glycol of chemical formula I, free of beta-hydrogenand a cycloaliphatic glycol. The alkylene glycol gives a greatcontribution to an improvement in UV stability and hydrolysis resistancewhile the cycloaliphatic glycol acts to prevent the lowering of theglass transition temperature of the composition and the hardness of thepaint coating in addition to restraining UV absorption.

In accordance with the present invention, these component materials arepolymerized to high molecular weight polyesters, which are greater thana specific molecular weight, with the aim of providing flexibility uponpress processing.

When the content of cycloaliphatic dicarboxylic acid in the acidiccomponent is greater than 40 mol %, the resin is too low in glasstransition temperature to secure appropriate hardness. On the otherhand, when the acidic component contains the aromatic dicarboxylic acidat an amount of more than 90 mol %, the coating materials show not onlyvery poor in flexibility but high viscous behavior which is notdesirable in paint.

In the alcohol component, 2,2-dialkyl-1,3-propanediol of chemicalformula I is contained at an amount of 60–100 mol %. For example, ifthis compound is used at an amount of less than 60 mol %, a significantdeterioration is brought about in the fluidity and hydrolysis resistanceof the resin. Particularly, a mixture of neopentylglycol and2-butyl-2-ethyl-1,3-propanediol can be used as the2,2-dialkyl-1,3-propanediol of chemical formula I. In this case, the2-butyl-2-ethyl-1,3-propanediol is present in the mixture in an amountof 10–55 mol % of the total amount of the alcohol component. Morepreferably, a mixture of neopentylglycol and2-butyl-2-ethyl-1,3-propanediol is used in an amount of 80–100 mol % ofthe total alcohol component, the 2-butyl-2-ethyl-1,3-propanediol beingpresent in an amount of 20–55 mol % of the total alcohol component. Inthis case, a more preferable effect is obtained in terms of hydrolysisresistance.

Also, there may be used a polyvalent alcohol which is selected from thegroup consisting of cyclohexanedimethanol, ethylene glycol, propyleneglycol, butanediol, 1,6-hexanediol, trimethylpentanediol,tricyclodecanedimethanol, and mixtures thereof. Particularly,cyclohexanedimethanol is used at an amount of 0–40 mol % and moreparticularly 20–30 mol % based on the moles of the total alcoholcomponent. For instance, when cyclohexanedimethanol is present at anamount larger than 40 mol % in the alcohol component, the paintcomposition shows such poor solubility in solvents and low fluidity andcoating smoothness that it cannot be used as a top-coating paint.1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and1,4-cyclohexanedimethanol, which may be used alone or in combination,exemplify useful cyclohexanedimethanol.

If the polyvalent alcohol is selected from the group consisting ofethylene glycol, butanediol, 1,6-hexanediol and mixtures thereof, itcomprises at most 20 mol % of the total alcohol component.

When polyfunctional component (c) having functionality three or higheris used for enhancing the reactivity of crosslinking and/or crosslinkingdensity by introducing branch structure into polyester, it should berestricted at an amount of at most 5 mol % and more particularly 0–2.5mol % based on the total moles of acid and alcohol components for thegood press processability. Those which have polyfunctional componenthaving functionality three or higher may be selected from the groupconsisting of trimethylolpropane, trimellitic acid or trimelliticanhydride and mixture thereof.

To be of excellent press processability, the copolyester of the presentinvention should have an intrinsic viscosity of 0.2 dl/g or morepreferably 0.20–0.40 dl/g, a number average molecular weight of5,000–20,000 and more preferably 6,000–12,000, an acid number of 0–3 mgKOH/g and an hydroxyl number of 20–50 mg KOH/g. A copolyester resin witha number average molecular weight of less than 5,000 has an increased,crosslink density, showing degraded press processability. On the otherhand, when the number average molecular weight is over 20,000, the resinshows a low hardness with a decrease of crosslink density. In this case,its solution viscosity is also elevated, thereby lowering the paintingworkability and making difficult the solidification of the paint coat toa high degree.

Non-limitative, illustrative examples of the esterification catalystsuseful in preparing the resin of the present invention include acetatesof Ca, Ce, Pb, Mn, Zn, Mg, and Sb, and tetrabutoxy titan. In the presentinvention, polycondensation may be conducted in the presence of Sb2O3 orGeO2. For the polycondensation, a phosphorus oxide may be usefully addedas a thermal stabilizer.

The copolyester resin of the present invention may be prepared in anordinary method. For example, a mixture of the acidic component and thepolyvalent alcohol component is gradually heated from room temperatureto about 200–260° C. in the presence of an esterification catalyst Whenby-products, such as water and methanol, are formed, the esters areadded with a polycondensation catalyst and a thermal stabilizer andreacted in a vacuum condition. At an elevated temperature of 260–280°C., the reactant is subjected to copolymerization for several hours togive copolyesters that have an intrinsic viscosity of 0.20–0.40 dl/g anda number average molecular weight of 6,000–12,000.

The copolyester resins according to the present invention areparticularly useful for coating compositions, such as paints. Forinstance, coating compositions formulated from the copolyester resinsshow excellent hardness, press processability and paint workability withsuperiority in weatherability, so they can be usefully applied fortop-coating paints for steel plates. Typically, a polyester-basedcoating composition comprises a solvent. It is possible to choose 1˜3species according to the each application or process condition in aratio of the main solvent to the co-solvent of 20˜50/80˜50. The mainsolvent may be selected from cyclohexanone, dibasic esters, cellosolveacetate, butyl glycol, etc. The co-solvent may be choosen from Solvesso#100 or Solvesso #150. The composition contains also a curing agent, ahardening agent, an anti-foaming agent, a wetting agent (for exampleNusperse 657(Tenneco) or BYK P104(BYK) or ASP-200 (Engelhard) orDISPARLON 2150 (KUSUMOTO, JAPAN) and/or other customary ordinaryadditives such as flowing and leveling agents (for example are 0.5% bytotal paint weight of Poly flow-S (KYOEISHA) or DISPARLON LC Series(KUSUMOTO) or URAD DD27 (DSM,Holland).

As for the curing agent, it is exemplified by a polyvalent isocyanatecuring agent, a thermal curing agent such as aminoformaldehyde or a urearesin. The ratio of crosslinker to copolyester varies from 1/4 to 1/9 inweight.

A better understanding of the present invention may be obtained in lightof the following examples that are set forth to illustrate, but are notto be construed to limit the present invention. In the followingexamples, physical and chemical properties were measured as follows:

Intrinsic Viscosity: measured at 35° C. in an ortho-chlorophenol solventby a Cannon-Ubbelodhe type viscometer.

Glass transition temperature: measured in a differential scanningcalorimetry (DSC) method.

Number Average Molecular Weight: solutions of copolyester resins intetrahydrofuran were subjected to gel permeation gas chromatography(WATERS GPC 150-CV) with polystyrene (Shodex SM-105′ from Showa Denko,Japan) serving as a control.

Solvent Resistance: a Zn-plated steel plate 0.5 mm thick, which wascoated with a paint and dried at 270° C. for 50 sec with the aid of ahot air dryer, was rubbed with a methylethylketone (MEK)-soaked gauzewhich was wrapped around a finger. When the rubbing was conducted insuch a manner that the gauze shuttled a distance of 10 cm on the plate,the solvent resistance was evaluated as the amount of the shuttlinguntil the paint coat was marred.

60° Gloss: when a beam was incident on a Zn-plated steel plate 0.5 mmthick, which was coated with a paint and dried at 270° C. for 50 secwith the aid of a hot air dryer, a reflectance at 60° from the plate wasmeasured by micro-tri Gloss meter, commercially available fromBYK-Gardener.

Accelerated Weatherability: a Zn-plated steel plate 0.5 mm thick, whichwas coated with a paint and dried at 270° C. for 50 sec with the aid ofa hot air dryer, was allowed to stand for 7,000 hours in a QUVaccelerated weathering tester, commercially available from Q-Panel, andits gloss retention percent was measured in comparison with the initialgloss. In the tester, the plate samples were allowed to repetitivelyundergo a testing cycle, which was composed of condensation for 4 hoursat 50° C., and QUV-A (340 nm) irradiation for 8 hours at 60° C.

Pencil Hardness: a Zn-plated steel plate 0.5 mm thick, which was coatedwith a paint and dried at 270° C. for 50 sec with the aid of a hot airdryer, was measured for coat hardness by use of a pencil for measuringcoat hardness, commercially available from Mitsubishi, Japan.

Flexibility: a Zn-plated steel plate 0.5 mm thick, which was coated witha paint and dried at 270° C. for 50 sec with the aid of a hot air dryer,was so completely bent as for bent plate halves to form an angle of zerodegree while plates with the same thickness were inserted between thebent halves. When no coat cracks were observed with a magnifying lens ata magnification of 30 times, the flexibility of the coat paint wasexpressed as the number of the plates inserted.

A. Preparation of Copolyester

EXAMPLES I TO VI

In a 500 ml three-necked flask equipped with a thermometer, a condenser,a mantle and a stirrer and connected to a vacuum pump, acid componentsand alcohol components were placed according to the indication of Table1, below. After being added with esterification catalysts, Zn acetateand tetrabutoxy titan, the components were gradually heated from roomtemperature to 250° C. When the by-product water or methanol wasdischarged to a theoretical amount, the polycondensation catalyst Sb2O3and the thermal stabilizer trimethyl phosphate were fed, after which thereactants were reacted at 265° C. for several hours in a vacuumcondition to give copolymers ranging, in intrinsic viscosity, from 0.20to 0.40 dl/g with a number average molecular weight of 6,000–12,000. Thecopolymers were measured for physical properties and the results aregiven in Table 1, below.

COMPARATIVE EXAMPLES I,II, III and IV

The same procedure as in Example I was repeated, except that acid andalcohol components were added as indicated in Table 1, below. Theproperties of the copolyesters obtained are given in Table 1.

TABLE 1 unit: wt (g) Compo- sitions & Prop- Example Comp. Exampleserties I II III IV V VI I II III IV Acid 1,2-cyclohexane 123.4 61.7123.4 123.4 30.8 123.4 154.2 0.0 154.2 0.0 Compo- dicarboxylic acidnent(a) 1,4-cyclohexane 0.0 0.0 0.0 0.0 103.3 0.0 0.0 0.0 103.3 0.0dicarboxylic acid Isophthalic Acid 199.4 265.8 199.4 199.4 199.4 199.40.0 166.1 66.5 332.3 Terephthalic Acid 0.0 0.0 0.0 0.0 0.0 0.0 166.1166.1 0.0 0.0 Alcohol Ethylene Glycol 37.2 37.2 37.2 37.2 37.2 9.3 41.041.0 31.1 37.2 Compo- 2,2-Dimethyl-1,3- 171.8 171.8 161.2 171.8 156.2148.4 165.6 165.6 156.2 171.8 nent (b) Propanediol 2-Butyl-2-ethyl-1,3-120.2 120.2 112.5 0.0 96.2 228.4 0.0 0.0 80.3 120.2 propanediolCyclohexane 0.0 0.0 0.0 108.2 0.0 0.0 0.0 0.0 0.0 0.0 dimethanol1,6-Hexanediol 0.0 0.0 0.0 0.0 35.5 0.0 70.9 70.9 59.2 0.0 Trimethylol0.0 0.0 20.1 0.0 0.0 0.0 20.1 20.1 0.0 0.0 Propane Prop- IntrinsicViscosity 0.239 0.353 0.345 0.302 0.294 0.312 0.290 0.311 0.303 0.339erties Tg (EC) 42.3 46.8 40.2 47.2 29.0 41.5 22.9 30.9 13.9 53.7 Number7473 10350 7061 8874 9600 9430 7000 6700 9500 10590 Average Mw

B. Preparation of Paints

To assay the performance of the present invention, each of thecopolyester synthesized in Examples I to VI and Comparative Examples Ito IV was dissolved in a mix solvent of cyclohexanone/Solvesso#100/Solvesso #150 (40/30/30) to give a solution with a solid content of50 wt % which was, then, formulated into a dispersion phase according tothe indication of Table 2. This dispersion phase was mixed as in Table3, to allow paint.

TABLE 2 Dispersion Formulation Phase TiO2 (Rutile type KRONOS-2160) 100g 50% resin solution DBE/Solvesso 100 g 100 = (1/1) mix solvent 50 gWetting Agent: Modaflow** 0.01 g **Available from Monsanto , U.S.A

TABLE 3 Solution Formulation Phase Dispersion Formulation (made with 250g Table 2) 50% resin solution* 71.4 g Cymel 303** 14.3 g n-butanol 8.1 gDinonynalenesulfonylacetate 50% 4.0 g Sol'n in cellosove acetate*Solvent system: cyclohexanone/Solvesso #100/Solvesso #150 (40/30/30)**Melamine formaldehyde cross-linker available from Cyanamid U.S.A.

C. Physical Properties of Coats

The paints thus obtained were coated on steel plates and the coats weremeasured for physical and chemical properties. The results are given inTable 4, below.

TABLE 4 Example Comp. example Coat Properties I II III IV V VI I II IIIIV Solvent over 50 49 41 over 50 46 50 Resistance (Rounds) 60° Gloss (%)89 91 87 91 88 90 71 85 88 86 Accelerated 79 87 81 76 62 88 11 16 70 86Weatherability (Gloss Retention %) Pencil Hardness H H 2 H H+ F F H H HB2 H Flexibility (T- 0 T 1 T 2 T 1 T 0 T 0 T 0 T 0 T 0 T 4 T BEND) Paintvis. (Ford 129 139 136 143 124 119 122 115 121 196 cup 4, sec)

As apparent from the data of the above examples and comparativeexamples, the copolyester resins prepared according to the presentinvention are superior in resistance to UV light and hydrolysis anduseful as binders for coating compositions which are used whereweatherability is required. Also, the binders provide the coatcompositions with assurance of processability, coat gloss, fluidity, andworkability, so that the coating compositions are very useful asoutdoor-durable top-coating paints for exterior finish materials, suchas steel plates.

The present invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of description rather than of limitation. Many modificationsand variations of the present invention are possible in light of theabove teachings. Therefore, it is to be understood that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

1. A copolyester resin for solventborne coating composition, saidcopolyester resin prepared by polycondensing components consistingessentially of: (a) an acid component comprising 60–90 mol % of aromaticdicarboxylic acid selected from the group consisting of isophthalicacid, C1–C2 alkylester of isophthalic acid, phthalic acid, C1–C2alkylester of phthalic acid, phthalic anhydride, and mixtures thereof,and 10–40 mol % of cycloaliphatic dicarboxylic acid selected from thegroup consisting of 1,2-cyclohexane dicarboxylic anhydride,1,2-cyclohexane dicarboxylic acid, C1–C2 alkylester of 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, C1–C2 alkylesterof 1,4-cyclohexane dicarboxylic acid, and mixtures thereof; (b) analcohol component comprising polyvalent alcohol present in an amount of40% or less, and 60–100 mol % of 2,2-dialkyl-1,3-propanediol whereinsaid polyvalent alcohol is selected from the group consisting ofcyclohexanedimethanol, propylene glycol, 2,2,4-trimethylpentanediol,tricyclodecanedimethanol, ethylene glycol, 2-methylpropanediol,butanediol, 1,6-hexanediol, and mixtures thereof, and said2,2-dialkyl-1,3-propanediol is the mixture of2-butyl-2-ethyl-1,3-propanediol and neopentyl glycol, and the2-butyl-2-ethyl-1,3-propanediol is present in an amount of 10–55 mol %of the total alcohol component; and (c) a polyfunctional componenthaving a functionality of three or higher, present in an amount of 5 mol% or less, based on the total moles of acid and alcohol components,wherein said polyfunctional component comprises polyacid, polyol, ormixtures thereof.
 2. The copolyester resin of claim 1, wherein the sumof the mixture of 2-butyl-2-ethyl-1,3-propanediol and neopentyl glycolcomprises 80–100 mol % of the total alcohol component, wherein said2-butyl-2-ethyl-1,3-propanediol is present in an amount of 20–55 mol %of the total alcohol component.
 3. The copolyester resin of claim 1,wherein said cyclohexanedimethanol is selected from the group consistingof 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, and mixtures thereof, wherein saidcyclohexanedimethanol is present in an amount less than or equal to 40mol % based on the total mole of the component (b).
 4. The copolyesterresin of claim 1, wherein said polyvalent alcohol is selected from thegroup consisting of ethylene glycol, butanediol, 1,6-hexanediol, andmixtures thereof, wherein said polyvalent alcohol is present in anamount less than or equal to 20 mol % of the total alcohol component. 5.The copolyester resin of claim 1, wherein polyfunctional component (c)is selected from the group consisting of trimethylolpropane, trimelliticacid, trimellitic anhydride, and mixtures thereof.
 6. The copolyesterresin of claim 1, wherein said copolyester has an acid value of 0–3 mgKOH/g, a hydroxyl value of 20–50 mg KOH/g, an intrinsic viscosity of 0.2dl/g or higher, and a number average molecular weight of 5,000–20,000.7. A solventborne coating composition comprising the copolyester of anyof claims 1, 2, or 3 to 6 and a crosslinking agent.
 8. The solventbornecoating composition according to claim 7, wherein the crosslinking agentis selected from the group consisting of aminoformaldehydes, urea, andblocked polyisocyanates resins.
 9. The solventborne coating compositionaccording to claim 7, further comprising a crosslinking catalyst and apigment.
 10. A coating produced by the solventborne coating compositionaccording to claim 7.